Polyester composition, films made thereof and process for producing the composition

ABSTRACT

A polyester composition includes a ligand capable of coordinating to a metal or metal ion, wherein the ligand includes at least one donor atom selected from the group consisting of a nitrogen atom, a sulfur atom, and an oxygen atom. Consequently, it is possible to inactivate a metal catalyst which adversely affects heat resistance. As a result, it is possible to obtain polyester compositions and films having excellent heat resistance, colorability, and weathering resistance. Moreover, in the process of producing a polyester, by separating and recovering a catalyst by adding a ligand which is capable of coordinating to a metal or metal ion and which includes at least one donor atom selected from the group consisting of a nitrogen atom, a sulfur atom, and an oxygen atom, it is possible to improve the heat resistance of the polyester composition.

TECHNICAL FIELD

The present invention relates to polyester compositions having excellentheat resistance, colorability, and weathering resistance which are usedas magnetic materials, packaging materials, optical materials, electricmaterials, etc., to polyester films, and to methods for producingpolyester compositions.

BACKGROUND ART

Polyester films, polyethylene terephthalate films in particular, havingexcellent mechanical characteristics, thermal characteristics, andelectrical characteristics, are widely used in various industrial fieldsand are in increasing demand. However, as the applications broaden andthe demands increase, there is a greater need for improvements in thecharacteristics and productivity of polyesters. Therefore, althoughpolyester films are produced for various purposes, such as forindustrial use and for magnetic material use, there are many problems tobe solved.

In general, when a polyester film is formed, a polymer produced bypolymerization is melted again to form the polyester film. There isresidence time in the process in which the polymer is melted again andmelt extrusion is performed. The polymer deteriorates during theresidence time, resulting in an increase in filter pressure due toclogging of the filter and defects in the film product, thus giving riseto problems. Pyrolysis, oxidative degradation, hydrolysis, etc., of thepolymer are considered to be the reasons for the above, and it issupposed that a metal catalyst present in the system promotes theoxidative degradation and hydrolysis of the polymer.

In order to improve productivity in the film-forming process, desirably,a film is electrostatically charged and brought into close contact witha casting drum when cooling and setting are performed. In order toperform casting by the electrostatic casting method, a metal at apredetermined amount or more is desirably added to the polymer. However,although productivity is improved by the addition of the metal, heatresistance is degraded because the metal acts as a degradation catalyst,which is undesirable. It is known that, in order to improve heatresistance, preferably, the metal additive is inactivated or a portionof the metal is removed. However, with respect to a currently knownmethod in which metal additive is inactivated using a phosphoruscompound, although the metal can be inactivated, the electrostaticadhesion between the molten film and the casting drum is decreased,which is problematic.

Furthermore, Japanese Unexamined Patent Application Publication No.2000-34343 discloses a method for recovering and removing a catalystfrom ethylene glycol produced in a polycondensation step. However, noproposition has been made on recovery and removal of a metal catalystfrom a polyester composition.

As described above, there are no known methods by which it is possibleto remove or inactivate a metal catalyst, which adversely affects heatresistance, without decreasing electrostatic adhesion between a moltenfilm and a casting drum.

DISCLOSURE OF INVENTION

A polyester composition or a polyester film according to the presentinvention includes a ligand capable of coordinating to a metal or metalion, wherein the ligand includes at least one donor atom selected fromthe group consisting of a nitrogen atom, a sulfur atom, and an oxygenatom.

A method for producing a polyester composition according to the presentinvention includes, in the process of producing a polyester, a step ofseparating and recovering a catalyst by adding a ligand which is capableof coordinating to a metal or metal ion and which includes at least onedonor atom selected from the group consisting of a nitrogen atom, asulfur atom, and an oxygen atom.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below.

A polyester composition of the present invention includes a ligandcapable of coordinating to a metal or metal ion, wherein the ligandincludes at least one donor atom selected from the group consisting of anitrogen atom, a sulfur atom, and an oxygen atom.

The polyester composition of the present invention may be produced by amethod in which a dialkyl ester is used as an acid component, and afterinitiating a transesterification reaction of the dialkyl ester with adiol component, a polycondensation step is performed by heating thereaction product under reduced pressure to eliminate an excess diolcomponent. Alternatively, the polyester composition may be produced bydirect polymerization using a dicarboxylic acid as an acid component.

The ligand used in the present invention is preferably a clathratecompound. Preferred examples of the ligands used in the presentinvention include linear polyether amides, cyclic polyethers, linearpolyethers, cyclic polyether polyesters, cyclic polyketones, cyclicpolyamines, cyclic polyamine polyamides, cyclic polythiaethers, azacrownethers, thiacrown ethers, cyclic azathiacrown ethers, azathiacrownethers, bicyclic cryptands, tricyclic cryptands, spherical cryptands,linear polyamines, and sulfur-containing ligands such as phosphorussulfide. Cyclodextrin is also a preferred ligand used in the presentinvention.

In the present invention, as the ligands, cyclic polyethers areparticularly preferred because they have a simple structure and havesuperior coordination linkage to metal ions in terms of entropy.Suitable ligands are 18-crown-6, 15-crown-5, 12-crown-4, 30-crown-10,dibenzo-18-crown-6, and dibenzo-30-crown-10 among the cyclic polyethers;pentaglyme, hexaglyme, and decane glyme among the linear polyethers;tetraamines, hexamethylene tetraamine (hexaamine), and pentaamines amongthe linear polyamines; phosphorus sulfide among the sulfur compounds;and [2,1,1], [2,2,1], [2,2,2], [3,2,2 ], [3,3,2], and [3,3,3] cryptandsas the bicyclic cryptands. Above all, 18-crown-6 is preferable becausestructural distortion does not occur and because six-coordination to ametal ion is enabled, and 30-crown-10 is also desirable becauseten-coordination to a metal or metal ion is enabled and it surrounds themetal or metal ion almost completely, resulting in stable conformation.

In order to inactivate the function of the metal or metal ion as thecatalyst, preferably, the ligand used in the present invention includesat least 4 donor atoms so that the active sites of the metal ion areblocked. If the number of donor atoms is 3 or less, the active sites ofthe metal, the number of active sites usually being 4 or more, may notbe blocked by the coordination. If the number of donor atoms exceeds 20,the ring structure becomes large, and as a result, the conformation forreceiving the metal or metal ion may be distorted, resulting indifficulty in trapping the metal or metal ion. Therefore, the number ofdonor atoms of the ligand is preferably 4 to 20, and more preferably, 6to 10.

In the present invention, when an alkali metal or alkaline-earth metalis mainly coordinated, the donor atom of the ligand is preferably anoxygen atom. The reason for this is that the oxygen atom, which has thehighest electronegativity among the oxygen atom, the nitrogen atom, andthe sulfur atom, can hold a metal having a small ionic radius, such asan alkali metal or alkaline-earth metal, more strongly by ionic bonding(ion-dipole interaction) in addition to covalent bonding. Furthermore,the oxygen atom can coordinate to a catalyst composed of a transitionmetal, such as antimony or germanium, and reverse reactions, that is,pyrolysis, oxidative degradation, and hydrolysis reactions of thepolymer, can be inhibited by the steric hindrance effect of the ligand.When the metal to which the ligand coordinates has a large ionic radius,such as in the case of a metal other than an alkali metal oralkaline-earth metal, since the covalent bond is stronger than the ionicbond, the nitrogen atom or sulfur atom is preferred.

The ligand used in the present invention is added in thepolycondensation step and the timing of addition is not particularlylimited. However, in order to inhibit the ligand from scattering, theligand is preferably added after esterification and transesterificationreactions or after polymerization, and in order to prevent the catalyticactivity from being decreased by the ligand, the ligand is preferablyadded after the transesterification reaction or after polymerization.

When,polyesters are produced, in general, (1) transesterificationcatalysts and polymerization catalysts and (2) compounds containingvarious metal elements to improve productivity by improvingelectrostatic characteristics are often added. Examples of (1) includeiron, antimony, titanium, aluminum, germanium, manganese, cobalt, zinc,copper, nickel, cadmium, and tin. Examples of (2) include lithium,sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium,strontium, and barium. Additionally, a large amount of a metal, such asmagnesium, may be added to accelerate the productivity by decreasing themelt resistivity and increasing the casting rate.

However, the metals or metal ions described above also acceleratedepolymerization reactions, such as decomposition, in addition to theacceleration of esterification reactions and polycondensation reactions.Therefore, in the present invention, by adding a predetermined ligandafter the esterification reaction or polycondensation reaction,depolymerization can be inhibited. With respect to a ligand capable ofcoordinating to a metal or metal ion, the metal or metal ion ispreferably at least one element selected from the group consisting oflithium, sodium, potassium, rubidium, cesium, beryllium, magnesium,calcium, strontium, barium, iron, antimony, titanium, aluminum,germanium, manganese, cobalt, zinc, copper, nickel, cadmium, and tin.The ligand of the present invention, as necessary, coordinates to thesemetals or metal ions, thus providing satisfactory performance.

When the ligand used in the present invention is added after thetransesterification reaction, a ligand which does not impair theactivity of the polycondensation catalyst metal must be used. As thepolycondensation catalyst metal, antimony trioxide, antimony pentaoxide,antimony acetate, germanium dioxide, germanium tetraethoxide, tetrabutyltitanate, or the like having an ionic radius of 0.53 to 1.00 Å is oftenused. For example, when germanium dioxide is used as thepolycondensation catalyst, the ionic diameter of the germanium ion is1.74 Å, and since oxygen atoms, etc., coordinate to the germanium ion inthe reaction system, the effective ionic radius is larger than that.Therefore, by using 12-crown-4 or 15-crown-5 having a hole size of 1.2 Åor 1.7 Å as the ligand, which is smaller than the germanium ion, theligand can only enclose the transesterification catalyst withoutenclosing germanium dioxide which is the polymerization catalyst.Furthermore, as necessary, the transesterification catalyst can beseparated and recovered from the polyester composition.

When the ligand used in the present invention is added afterpolycondensation, by using a ligand having a hole size close to theionic radius of the polycondensation catalyst metal and the ionic radiusof the transesterification catalyst, or by using a ligand which is knownto be highly capable of trapping ions, the catalysts can be enclosed,and, as necessary, the catalysts can be recovered from the polyestercomposition. Additionally, in the present invention, when a metal forimproving electrostatic attraction is added, preferably, the metal isenclosed in a clathrate compound beforehand so that only the ioniccharacter is retained.

In the present invention, the amount of ligand added is preferably 0.001to 10% by weight of the resultant polyester composition, and morepreferably, 0.01 to 5% by weight. If the content of the ligand is out ofthe range of 0.001 to 10% by weight, sufficient activity-inhibitingeffects and catalyst-eliminating effects may not be obtained. If thecontent of the ligand exceeds 10% by weight, the amount of ligand whichis by itself subjected to pyrolysis, mechanical decomposition, andoxidative degradation may become significant, resulting in a decrease inheat resistance.

In the present invention, when a ligand including only oxygen as thedonor atoms is used, because of the high affinity of the oxygen atom foralkali metals and alkaline-earth metals, with respect to an amount S[mol/ton-polymer] of the ligand relative to a total amount Ma[mol/ton-polymer] of alkali metals and alkaline-earth metals present inthe polyester resin, the molar ratio Rma=S/Ma is preferably in the rangeof 0.001 to 30, more preferably, 0.01 to 10, and most preferably, 0.1 to5.

When a ligand including only nitrogen and sulfur as the donor atoms isused, because of the high affinity of the nitrogen and sulfur atoms fortransition metals, with respect to the amount S [mol/ton-polymer] of theligand relative to a total amount Mt [mol/ton-polymer] of transitionmetals present in the system, the molar ratio Rmt=S/Mt is preferably inthe range of 0.001 to 30, more preferably, 0.01 to 10, and mostpreferably, 0.1 to 5.

Furthermore, when a ligand including all of nitrogen, sulfur, and oxygenas the donor atoms is used, with respect to the amount S[mol/ton-polymer] of the ligand relative to a total amount Ms[mol/ton-polymer] of all the metals present in the system, the molarratio Rms=S/Ms is preferably in the range of 0.001 to 30, morepreferably, 0.01 to 10, and most preferably, 0.1 to 5.

In the present invention, the melt resistivity of the polyestercomposition is preferably less than 15×10⁷ Ω·cm, and more preferably,less than 10×10⁷ Ω·cm. If the melt resistivity is 15×10⁷ Ω·cm or more,electrostatic casting cannot be performed satisfactorily, and air caneasily enter between the film and the casting drum during the meltextrusion casting. As a result, a decrease in the film-forming rate maybe necessitated. Herein, the melt resistivity is defined as the valuecalculated by measuring the current flow when a voltage is applied tothe polyester composition in the molten state, and is an index ofelectric conductivity.

In the present invention, the melt resistivity is preferably notincreased by the presence of the ligand. If the melt resistivity isincreased, electrostatic charging is degraded in the film-forming step,thus degrading the productivity of the film. Preferably, therelationship R/R0≦1.3 is satisfied, more preferably, R/R0≦1.1, and mostpreferably, R/R0≦1.0, wherein R is a melt resistivity when the ligand isadded, and R0 is a melt resistivity before the addition of the ligand.

In the present invention, preferably, the polyester composition includesethylene terephthalate or ethylene-2,6-naphthalate as a principalconstituent in view of heat resistance and mechanical characteristics.

In the polyester composition of the present invention, ascopolymerizable components, a dicarboxylic acid or an ester-formingderivative thereof and a diol may be copolymerized to providecharacteristics, such as heat resistance, high rigidity, andelectrostatic properties.

Examples of dicarboxylic acid components copolymerizable in thepolyester composition of the present invention are isophthalic acid,phthalic acid, 1,4-naphthalenedicarboxylic acid,1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,4-4′-diphenyldicarboxylic acid, 4-4′-diphenyletherdicarboxylic acid, and4-4′-diphenylsulfonedicarboxylic acid, or ester-forming derivativesthereof.

Examples of diol components are aliphatic, alicyclic, and aromaticdiols, such as ethylene glycol, 1,2-propanediol, neopentyl glycol,1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol,polyalkylene glycols, and 2,2-bis(4′-β-hydroxyethoxyphenyl)propane.These components may be used alone or in combination.

Additionally, examples of the alicyclic dicarboxylic acid componentscopolymerizable in the polyester composition of the present inventioninclude 1,4-cyclohexanedicarboxylic acid. Aliphatic dicarboxylic acids,such as sebacic acid and dimer acids, and other dicarboxylic acids mayalso be used as copolymerizable components.

In the esterification and transesterification reactions, variouscatalysts may be used. For example, acetates, such as calcium acetate,magnesium acetate, and lithium acetate, and titanium compounds, such astitanium tetraethylene glycoxide, may be used.

Examples of polymerization catalysts that can be used are antimonytrioxide, antimony pentaoxide, germanium dioxide, germaniumtetrabutoxide, germanium tetraethoxide, titanium tetraethyleneglycoxide, and tetrabutyl titanate.

In the present invention, a stabilizer may be added in thepolycondensation step in order to prevent side reactions, such aspyrolysis of the polyester. Examples of stabilizers that can be used aretetrakis{methylene-3-(dodecylthio)propionate}methane,tetrakis{methylene-(3,5-t-butyl-4-hydroxyhydrocinnamate)}methane,tridecylphosphate, tris(2,4-dibutylphenyl)phosphite, andtetrakis{methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate)methane.These substances may be used alone or in combination. The amount of thestabilizer to be added is preferably 0.03 to 2% by weight of theresultant polyester composition, and more preferably, 0.05 to 1.9% byweight. If the amount of the stabilizer to be added is less than 0.03%by weight, the oxidation stability-improving effect may be decreased, orif the amount of the stabilizer exceeds 2% by weight, thepolycondensation reaction may be hampered.

In the present invention, if a small amount of a basic compound is addedin the esterification step, it is possible to obtain a polyestercomposition with a low content of side reaction products. Examples ofsuch a basic compound are tertiary amines, such as triethylamine,tributylamine, and benzylmethylamine, and quaternary amines, such astetraethylammonium hydroxide, tetrabutylammonium hydroxide, andtrimethylbenzylammonium hydroxide.

The polyester composition of the present invention may be formed into afilm by a melt extrusion method. That is, after the polyestercomposition is dried, the polyester composition is fed into asingle-screw or twin-screw extruder provided with a T-die and isextruded on a casting drum at the melting temperature of the polyester,and electrostatic casting is performed to produce an unoriented film. Inorder to obtain an oriented polyester film, the unoriented film isfurther drawn by sequential biaxial orientation or simultaneous biaxialorientation, followed by heat treatment.

The polyester composition of the present invention alone may be formedinto a film, or the polyester composition of the present invention maybe mixed with another polyester composition to form a film. In somecases, in order to improve productivity and heat resistance, 1% byweight or more of the polyester composition of the present invention ispreferably mixed with another polyester composition to form a film.

It is also possible to form a laminated film having a structureincluding a layer composed of the polyester composition of the presentinvention and a layer composed of another polyester composition so thatthe laminated film has combined characteristics of the individuallayers. In order to produce the laminated film of the present invention,for example, after the polyester composition of the present inventionand another polyester composition are dried, according to a commonlyused method, a combined block including at least two rectangularlamination layers is melt-extruded from a die to form an unorientedsheet so that the individual layers are laminated at a predeterminedthickness ratio and with a predetermined construction, and then biaxialdrawing and heat treatment are preformed.

When the polyester composition of the present invention is subjected tobiaxial drawing, although the draw ratio is not particularly limited,the draw ratio is usually 2 to 5 times in each of the longitudinal andtransverse directions. Furthermore, after longitudinal drawing andtransverse drawing are performed, redrawing may be performed either inthe longitudinal direction or in the transverse direction, orsimultaneous biaxial drawing may be performed. When an easy adhesionlayer, a particle layer, etc., are formed, coating components may beapplied in-line before drawing or between longitudinal drawing andtransverse drawing. Alternatively, off-line coating may be performedafter drawing.

In a method for producing a polyester composition according to thepresent invention, in the process of producing a polyester including anesterification step using an esterification catalyst and/or apolycondensation step using a polycondensation catalyst, theesterification catalyst and the polycondensation catalyst are separatedand recovered by adding a ligand which is capable of coordinating to ametal or metal ion and which contains at least one donor atom selectedfrom the group consisting of a nitrogen atom, a sulfur atom, and anoxygen atom.

In the method for producing the polyester composition of the presentinvention, for example, a dicarboxylic acid or an ester thereof and aglycol are used as raw materials.

In the present invention, in the esterification step and/or thepolycondensation step, a distillate which is retrieved from the systemis usually generated. The distillate contains 100 to 800 ppm, calculatedon the basis of metal atomic weight, of catalysts, 4 to 20% by weight ofwater, 80 to 96% by weight of the glycol component, 0.3 to 5% by weightof the lower condensate (cyclic trimer) of the polyester, and 0.01 to10% by weight of the ligand, in addition to stabilizers, iron, etc.

In the method for producing the polyester composition of the presentinvention, it is possible to recover the esterification catalyst and thepolycondensation catalyst from the distillate which is retrieved fromthe system in the esterification step and/or the polycondensation step.

In the method for producing the polyester composition of the presentinvention, for example, after an aqueous solution having a higheraffinity for cations compared to the ligand is added to the retrieveddistillate to remove the metal from the ligand, a distillation step isperformed to eliminate the water, low-boiling point components, theglycol, and the ligand, and simultaneously a residual catalyst isreacted with the glycol to produce a coordination compound including theglycol. By this step, a solution containing the water, the low-boilingpoint components, the glycol, and the ligand and a solid residuecontaining the catalyst are separated from each other. The solutioncontaining the water, the low-boiling point components, the glycol, andthe ligand is dissolved in an organic solvent, and purification isperformed by the addition of activated carbon. The insoluble residue isfiltered out, and water is added to the filtrate, followed by mixing. Aprecipitated solid is then separated by filtration, and cleaning isperformed with water and ethanol, followed by drying to recover theligand. The solid residue is further fractionated by a hot waterdissolution step into a solid residue and a lower condensate, thestabilizer, and iron which are insoluble in water. Since substancesother than the catalysts are insoluble in water, by filtering thesesubstances out, followed by condensation, the catalysts can berecovered.

The catalysts thus recovered are retrieved as solids and can be used asadditives in the esterification step and the polycondensation step inthe same manner as the unused catalysts, and the quality of thepolyester is not degraded.

On the other hand, in the metal or metal ion which is coordinated withthe ligand described in the present invention, since the catalyticactivity for decomposing the polyester is decreased, degradation in heatresistance by the metal or metal ion is decreased, thus improving theheat resistance of the polyester resin.

Moreover, with respect to the polyester composition of the presentinvention, electrostatic casting capability is not substantiallydegraded in the film-forming step. The reason for this is considered tobe that the metal or metal ion which is coordinated to the liganddescribed in the present invention loses its catalytic activity whileretaining its electric characteristics, or differing from the ionicbond, the ligand which is not strongly bonded to the metal ion isdissociated from the metal ion because of the high voltage duringelectrostatic charging, thus exhibiting its electric characteristics.

Inorganic particles or organic particles may be added to the polyestercomposition of the present invention as necessary. The inorganicparticles to be added are not particularly limited, and compounds, suchas silica, alumina, calcium carbonate, titanium oxides, calciumphosphates, hydroxyapatite, and aluminum silicate, may be used. Examplesof the organic particles include crosslinked polymer particles.

In the method for producing the polyester composition of the presentinvention, by removing a portion of the metal contained in the polyestercomposition, the heat resistance of the polyester composition isimproved, and colorability, weathering resistance, and productivity arealso improved. In accordance with the method for producing the polyestercomposition of the present invention, polyester compositions suitablefor various applications, such as for magnetic materials, packagingmaterials, optical materials, and electric materials, can be produced.

The polyester composition, the method for producing the polyestercomposition, and the film in accordance with the present invention haveexcellent heat resistance, colorability, and weathering resistance andare suitable for various applications, such as for magnetic materials,packaging materials, optical materials, and electric materials.

EXAMPLES

The present invention will be described in more detail based on theexamples below. The individual properties in the examples were measuredby the following methods.

(1) Measurement of Ligand Content (% by Weight)

After 100 mg of a composition sample was dissolved in 2 ml ofhexafluoroisopropanol as a solvent, the mixture was left to stand forone night and dissolved in 1 ml of CDCl₃, and data obtained by a nuclearmagnetic resonance method using a 400 MHz, ¹H-NMR (Model GX-400 pulse FTspectrometer manufactured by JOEL) and a 22.5 MHz, ¹³C-NMR (Model FT-900pulse FT spectrometer manufactured by JOEL) were analyzed to obtain theligand content.

(2) Intrinsic Viscosity of Polymer ([η] (dL/g))

Measurement was conducted at 25° C. using o-chlorophenol as a solvent.

(3) Heat Resistance of Polymer (% BB) (Melt Heat Test)

A polymer in the quantity of 8 g was placed in a test tube, heattreatment was performed in a nitrogen atmosphere at a pressure of 0.1MPa at 300° C., for 10 minutes (t₀), 3 hours (t), and 6 hours (t), andthe respective values η were measured. Heat resistance was calculatedaccording to the following equation:%BB _(t)=(1/[η]_(t) ^((1/0.75))−1/[η]_(t0) ^((1/0.75)))

wherein [η]_(t) is a value when heat treatment was performed for 3 hoursor 6 hours, and [η]_(t0) is a value when heat treatment was performedfor 10 minutes.

In the case of a film, the same method as that for the polymer describedabove was used apart from the fact that 8 g of the film was placed in atest tube and melted.

(4) Melt Resistivity

Electrodes were formed by placing a Teflon spacer between two copperplates, each with a size of 22 cm², the distance between the copperplates being 9 mm. The electrodes were immersed in a polymer melted at290° C., and a resistance was calculated based on a current measuredwhen a voltage of 5,000 V was applied between the electrodes.

(5) Metal Content (FLX)

A polymer in the quantity of 8 g was melted and molded into a plate, andthe intensity of fluorescence X-rays was measured. The value measuredwas converted into the metal content using an analytical curve which waspreliminarily prepared using samples with known contents.

(6) Metal Content (Atomic Absorption Spectrometry)

Alkali metals were measured by atomic absorption spectrometry. Using ahollow cathode lamp as a light source, 8 g of a polymer was atomized byflame atomization, and detection was performed by a photometric unit.The value measured was converted into the metal content using ananalytical curve which was preliminarily prepared.

Example 1

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.04 parts by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020 parts by weight of trimethylphosphate, relative to the amount of dimethylterephthalate, was added tothe transesterification product, and 0.02 parts by weight of germaniumoxide was then added thereto. The mixture was transferred to apolycondensation reaction vessel. Next, the pressure of the reactionsystem was gradually decreased while heating, and under reducedpressure, at 290° C., polymerization was performed while stirring themixture and distilling methanol off. When the degree of polymerizationreached the equivalent of an intrinsic viscosity of 0.62, the system waspurged with nitrogen and the pressure was returned to the atmosphericpressure, and then, 0.06 parts by weight of potassium acetate and anethylene glycol solution of 18-crown-6 (10 mol % relative to the metalcontent excluding the metal contained in particles) were thoroughlymixed and added thereto. The pressure of the reaction system wasgradually decreased, and under reduced pressure, at 290° C.,polymerization was performed again in the same manner as that describedabove. When the degree of polymerization reached the equivalent of anintrinsic viscosity of 0.62, discharge was performed at a predeterminedtorque, and a polyester composition (W) with an intrinsic viscosity of0.60 was thereby obtained. The results thereof are shown in Table 1below. As shown in Table 1, the measured 18-crown-6 content in thepolyester composition was 8.3 mol %, and the amount (Rma) of ligandrelative to the metals was 0.083.

Comparative Example 1

A polyethylene terephthalate (PL) chip with [η]=0.60 was obtained in thesame manner as that of Example 1 apart from the fact that theequimolecular amount of ethylene glycol was added instead of 18-crown-6.The results thereof are shown in Table 1.

Reference Example 1

A polyester (S) chip containing particles with [η]=0.61 was obtained inthe same manner as that of Comparative Example 1 apart from the factthat before the mixture was transferred to the polycondensation reactionvessel, an ethylene glycol slurry containing 5% by weight of silicaparticles having an average particle size of 0.05 μm was added in thequantity of 1% by weight as particles relative to the amount ofdimethylterephthalate.

Example 2

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that the equimolecular amount ofdibenzo-18-crown-6 was used instead of 18-crown-6. The results thereofare shown in Table 1.

Example 3

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that the equimolecular amount ofdibenzo-30-crown-10 was used instead of 18-crown-6. The results thereofare shown in Table 1.

Example 4

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that the equimolecular amount ofpentaglyme was used instead of 18-crown-6. The results thereof are shownin Table 1.

Example 5

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that the equimolecular amount ofhexadecane glyme was used instead of 18-crown-6. The results thereof areshown in Table 1.

Comparative Example 2

A polyethylene terephthalate (K) chip with [η]=0.60 was obtained in thesame manner as that of Example 1 apart from the fact that theequimolecular amount of ethylene glycol was added instead of each ofpotassium acetate and 18-crown-6. The results thereof are shown in Table1.

TABLE 1 Amount of ligand Amount of (mol %) ligand Number Melt (to (to ofresistivity Metal) Metal) % BB donor R Ligand *1 Rma 3 hours 6 hoursatoms (×10⁷ Ω · cm) R/R0 Example 1 18-crown-6 8.3 0.083 0.42 0.64 6 7 1Example 2 Dibenzo- 7.7 0.077 0.45 0.67 6 7 1 18-crown-6 Example 3Dibenzo- 7.3 0.073 0.40 0.62 10 7 1 30-crown- 10 Example 4 Pentaglyme9.6 0.096 0.45 0.68 5 7 1 Example 5 Hexadecane 9.2 0.092 0.41 0.65 16 71 glyme Comparative No ligand — 0.49 0.76 7 1 Example 1 Comparative Noligand — 0.48 0.65 16 1 Example 2 *1: Amount of ligand relative to totalamount of alkali metals and alkaline-earth metals

Example 6

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that 1.7% by weight of 18-crown-6 wasadded so that the amount added relative to the total amount of alkaliand alkali-earth metals satisfied Rma=3.0. The results thereof are shownin Table 2.

Example 7

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that, instead of 18-crown-6, 0.08% byweight of hexaamine was added so that the amount added relative to thetotal amount of transition metals satisfied Rmt=3.0. The results thereofare shown in Table 2.

Example 8

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that, instead of 18-crown-6, 0.26% byweight of phosphorus sulfide was added so that the amount added relativeto the total amount of transition metals satisfied Rmt=3.0. The resultsthereof are shown in Table 2.

Example 9

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that, instead of 18-crown-6, 1.12% byweight of [2,2,2] cryptand was added so that the amount added relativeto the total amount of alkali and alkali-earth metals and transitionmetals satisfied Rms=3.0. The results thereof are shown in Table 2.

Comparative Example 3

A polyester composition was obtained in the same manner as that ofExample 1 apart from the fact that, instead of 18-crown-6, 0.07% byweight of sodium bisulfate was added so that the amount added relativeto the total amount of transition metals satisfied Rmt=3.0. The resultsthereof are shown in Table 2.

TABLE 2 Amount of Number Melt ligand of resistivity (to Metal) % BBdonor R Ligand Rma, Rms, Rmt 3 hours 6 hours atoms (×10⁷ Ω · cm) R/R0Example 6 18-crown-6 Rma = 3.0 0.41 0.62 6 7 1 Example 7 Hexaamine Rmt =3.0 0.45 0.67 4 7 1 Example 8 Phosphorus Rmt = 3.0 0.44 0.66 6 7 1sulfide Example 9 [2,2,2]cryptand Rms = 3.0 0.40 0.63 8 7 1 ComparativeNo ligand — 0.42 0.64 — 20 2.86 Example 3

Example 10

The polyester composition (W) obtained in Example 1 was thoroughlydried, fed into an extruder, and melt-extruded on a casting drum. Fusionbonding was performed while electrostatically charging the casting drum,and quench hardening was performed to produce a single-layer unorientedfilm. The unoriented film was then drawn, 3.5 times in the longitudinaldirection at 90° C. and 3.5 times in the transverse direction at 105°C., and a polyester film with a thickness of 10 μm was thus obtained.Satisfactory film formability was exhibited. The film thus obtained hadsatisfactory heat resistance and productivity. The results thereof areshown in Table 3.

Example 11

A polyester film was obtained in the same manner as that of Example 10apart from the fact that the polyester composition (W) obtained inExample 1, the polyethylene terephthalate (PL) obtained in ComparativeExample 1, and the polyester (S) containing particles obtained inReference Example 1 were thoroughly dried and dry blended so that theligand content relative to the metal content (excluding the metalcontained in particles) corresponded to the content (Rma=0.0021) shownin Table 3. The results thereof are shown in Table 3.

Example 12

The polyester composition (W) obtained in Example 1 and the polyethyleneterephthalate (PL) obtained in Comparative Example 1 were thoroughlydried and dry blended so that the ligand content relative to the metalcontent (excluding the metal contained in particles) corresponded to thecontent (Rma=0.052) shown in Table 3. The mixture was fed into a primarylayer (layer A) extruder. The polyester (S) containing particlesobtained in Reference Example 1 was dried and dry blended withpolyethylene terephthalate (PL) so that the particle content was 0.5% byweight. The mixture was fed into a secondary layer (layer B) extruder.Melt extrusion was performed through a two-layer die onto a castingdrum, and fusion bonding was performed while electrostatically chargingthe casting drum, followed by quench hardening. An A/B type (thicknessratio 6/1) two-layer unoriented film was thus obtained. Next, theunoriented film was drawn at 90° C., 3.5 times in the longitudinaldirection, and at 105° C., 3.5 times in the transverse direction, and alaminated polyester film with a thickness of 8 μm was thus obtained(thickness of layer B: 1.33 μm). Satisfactory film formability wasexhibited. The film thus obtained had satisfactory heat resistance andproductivity. The results thereof are shown in Table 3.

Example 13

A laminated polyester film was obtained in the same manner as that ofExample 12 apart from the fact that the polyester composition (W)obtained in Example 1, the polyethylene terephthalate (PL) obtained inComparative Example 1, and the polyester (S) containing particlesobtained in Reference Example 1 were blended and fed into an extruder sothat the ligand content relative to the metal content (excluding themetal contained in particles) in the layer A and the layer Bcorresponded to the content shown in Table 3 (layer A: Rma=0.015, layerB: Rma=0.000). The results thereof are shown in Table. 3.

Example 14

A laminated polyester film was obtained in the same manner as that ofExample 12 apart from the fact that the polyester composition (W)obtained in Example 1, the polyethylene terephthalate (PL) obtained inComparative Example 1, and the polyester (S) containing particlesobtained in Reference Example 1 were blended and fed into an extruder sothat the ligand content relative to the metal content (excluding themetal contained in particles) in the layer A and the layer Bcorresponded to the content shown in Table 3 (layer A: Rma=0.053, layerB: Rma=0.032). The results thereof are shown in Table 3.

Comparative Example 4

A film was formed in the same manner as that of Example 12 apart fromthe fact that the polyethylene terephthalate (PL) obtained inComparative Example 1 was fed instead of the polyester composition (W)obtained in Example 1. Poor heat resistance was exhibited andproductivity was degraded. The results thereof are shown in Table 3.

Comparative Example 5

A film was formed in the same manner as that of Example 10 apart fromthe fact that the polyethylene terephthalate (K) obtained in ComparativeExample 2 was fed instead of the polyester composition (W) obtained inExample 1. Although heat resistivity was satisfactory, melt resistivitywas increased and productivity was degraded. The results thereof areshown in Table 3.

Comparative Example 6

A laminated polyester film was obtained in the same manner as that ofExample 12 apart from the fact that a polyethylene terephthalate chipwith [η]=0.60 was produced in the same manner as that of Example 1except that diethylene glycol was used instead of 18-crown-6, and thepolyethylene terephthalate (PL) obtained in Comparative Example 1 andthe polyester (S) containing particles obtained in Reference Example 1were blended and fed into an extruder. The results thereof are shown inTable 3.

TABLE 3 Lamination structure Layer A Layer B Amount of Amount of ligandAmount of ligand Amount of (mol %) ligand (mol %) ligand Number Melt (to(to (to (to of resistivity Metal) Metal) Metal) Metal) % BB donor RLigand *1 Rma *1 Rma 3 hrs 6 hrs atoms (×10⁷ Ω · cm) R/R0 Example 10 18-8.3 Rma = — 0.50 0.68 6 7 1 crown-6 0.083 Example 11 18- 2.1 Rma = —0.55 0.77 6 7 1 crown-6 0.021 Example 12 18- 5.2 Rma = 0.0 Rma = 0.520.74 6 7 1 crown-6 0.052 0.000 Example 13 18- 1.5 Rma = 0.0 Rma = 0.550.78 6 7 1 crown-6 0.015 0.000 Example 14 18- 5.3 Rma = 3.2 Rma = 0.510.75 6 7 1 crown-6 0.053 0.032 Comparative No — — 0.59 0.86 — 7 1Example 4 ligand Comparative No — — 0.50 0.74 — 16 1 Example 5 ligandComparative No — — 0.63 0.85 — 7 1 Example 6 ligand *1: Amount of ligandrelative to total amount of alkali metals and alkaline-earth metals

Example 15

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.04% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product, and 0.007% by weight of germanium dioxidewas then added thereto. The mixture was transferred to apolycondensation reaction vessel. Next, the pressure of the reactionsystem was gradually decreased while heating, and under a reducedpressure of 133 Pa, at 290° C., polymerization was performed whilestirring and distilling methanol off. When the degree of polymerizationreached the equivalent of an intrinsic viscosity of 0.62, the system waspurged with nitrogen and the pressure was returned to the atmosphericpressure. Next, 0.03% by weight of potassium acetate and 0.2% by weightof an ethylene glycol solution of 18-crown-6 were thoroughly mixed andadded thereto. The pressure of the reaction system was graduallydecreased, and under a reduced pressure of 133 Pa, at 290° C.,polymerization was performed again in the same manner as that describedabove. When the degree of polymerization reached the equivalent of anintrinsic viscosity of 0.62, discharge was performed at a predeterminedtorque, and a polyester composition with an intrinsic viscosity of 0.60was thereby obtained. The results thereof are shown in Table 4 below. InTable 4, the amount of metal added means the amount of metal addedbefore repolymerization, and the metal content means the amount of metalin the resultant polyester composition. The difference between theamount of metal added and the metal content corresponds to the amount ofmetal removed.

Metal ions and ligands were separated and recovered from the distillate,which was retrieved from the system in the polycondensation step, by amethod described below. After HNO₃ was added to the distillate so as tosatisfy pH=1.5, water, low-boiling point components, and ethylene glycolwere removed by distillation at 210° C. at 1,330 Pa for 4 hours, and asolid residue was separated. Into the low-boiling point components, 400parts by weight of ethanol, 30 parts by weight of potassium acetate, and10 parts by weight of activated carbon were added, followed by mixing atroom temperature. Impurities generated were filtered out, and 1,000parts by weight of water were added to the filtrate. A precipitatedsolid was then separated by filtration, and cleaning was performed withwater and ethanol, followed by drying. A white powder (18-crown-6) wasthereby obtained. To the solid residue, 100 parts by weight of purifiedwater was added, and the solid residue was dissolved by heating at 95°C. at atmospheric pressure for 2 hours. Insoluble components werefiltered out at 50° C. using a membrane filter (5.0 μm). The filtratecontained 500 ppm, calculated on the basis of germanium atomic weight,of the germanium catalyst, 50 ppm of the magnesium catalyst, and 3,000ppm of the potassium catalyst. The resultant filtrate was condensed at95° C. at 55,000 Pa for 2 hours and an aqueous solution containing 1.5%by weight of germanium, 9% by weight of potassium, and 0.15% by weightof magnesium was formed. Acetic acid and ethylene glycol (EG) were addedthereto and azeotropic distillation was performed to form an EG solution(mixed catalyst) containing 4.5% by weight of germanium, 18% by weightof potassium, and 0.45% by weight of magnesium.

Example 16

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.038% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product. The mixed catalyst recovered in Example 15was added thereto so that the amount of potassium acetate was 0.03% byweight, and 0.0042% by weight of germanium dioxide was further addedthereto. The mixture was transferred to a polycondensation reactionvessel. Next, the pressure of the reaction system was graduallydecreased while heating, and under reduced pressure, at 290° C.,polymerization was performed while stirring and distilling methanol off.When the degree of polymerization reached the equivalent of an intrinsicviscosity of 0.62, the system was purged with nitrogen and the pressurewas returned to the atmospheric pressure. An ethylene glycol solution ofthe 18-crown-6 recovered in Example 1 was prepared and thoroughly mixed,and 0.2% by weight thereof was added to the reaction system. Thepressure of the reaction system was gradually decreased, and underreduced pressure, at 290° C., polymerization was performed again in thesame manner as that described above. When the degree of polymerizationreached the equivalent of an intrinsic viscosity of 0.62, discharge wasperformed at a predetermined torque, and a polyester composition with anintrinsic viscosity of 0.60 was thereby obtained. The results thereofare shown in Table 4. In Table 4, the amount of metal added means theamount of metal added before repolymerization, and the metal contentmeans the amount of metal in the resultant polyester composition. Thedifference between the amount of metal added and the metal contentcorresponds to the amount of metal removed.

Example 17

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.04% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product, and then 0.007% by weight of antimonytrioxide was added thereto. The mixture was transferred to apolycondensation reaction vessel. Next, the pressure of the reactionsystem was gradually decreased while heating, and under reducedpressure, at 290° C., polymerization was performed while stirring anddistilling methanol off. When the degree of polymerization reached theequivalent of an intrinsic viscosity of 0.62, the system was purged withnitrogen and the pressure was returned to the atmospheric pressure.Potassium acetate in the amount of 0.03% by weight and an ethyleneglycol solution of dibenzo-18-crown-6 in the amount of 0.2% by weightwere thoroughly mixed and added to the system. The pressure of thereaction system was gradually decreased, and under reduced pressure, at290° C., polymerization was performed again in the same manner as thatdescribed above. When the degree of polymerization reached theequivalent of an intrinsic viscosity of 0.62, discharge was performed ata predetermined torque, and a polyester composition with an intrinsicviscosity of 0.60 was thereby obtained. The results thereof are shown inTable 4. In Table 4, the amount of metal added means the amount of metaladded before repolymerization, and the metal content means the amount ofmetal in the resultant polyester composition. The difference between theamount of metal added and the metal content corresponds to the amount ofmetal removed.

Example 18

A polyester composition was obtained in the same manner as that ofExample 15 apart from the fact that, instead of 18-crown-6, theequivalent weight percent of dibenzo-30-crown-10 was added. The resultsthereof are shown in Table 4. In Table 4, the amount of metal addedmeans the amount of metal added before repolymerization, and the metalcontent means the amount of metal in the resultant polyestercomposition. The difference between the amount of metal added and themetal content corresponds to the amount of metal removed.

Example 19

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.04% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product, and 0.007% by weight of germanium dioxidewas then added thereto. The mixture was transferred to apolycondensation reaction vessel. Next, the pressure of the reactionsystem was gradually decreased while heating, and under reducedpressure, at 290° C., polymerization was performed while stirring anddistilling methanol off. When the degree of polymerization reached theequivalent of an intrinsic viscosity of 0.62, the system was purged withnitrogen and the pressure was returned to the atmospheric pressure.Next, an ethylene glycol solution of 12-crown-4 was thoroughly mixed and0.2% by weight thereof was added to the reaction system. The pressure ofthe reaction system was gradually decreased, and under reduced pressure,at 290° C., polymerization was performed again in the same manner asthat described above. When the degree of polymerization reached theequivalent of an intrinsic viscosity of 0.62, discharge was performed ata predetermined torque, and a polyester composition with an intrinsicviscosity of 0.60 was thereby obtained. The results thereof are shown inTable 4. In Table 4, the amount of metal added means the amount of metaladded before repolymerization, and the metal content means the amount ofmetal in the resultant polyester composition. The difference between theamount of metal added and the metal content corresponds to the amount ofmetal removed.

Example 20

A polyester composition was obtained in the same manner as that ofExample 15 apart from the fact that, instead of 18-crown-6, theequivalent weight percent of 15-crown-5 was added. The results thereofare shown in Table 4. In Table 4, the amount of metal added means theamount of metal added before repolymerization, and the metal contentmeans the amount of metal in the resultant polyester composition. Thedifference between the amount of metal added and the metal contentcorresponds to the amount of metal removed.

Example 21

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.04% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product, and 0.007% by weight of germanium dioxidewas then added thereto. The mixture was transferred to apolycondensation reaction vessel. Next, the pressure of the reactionsystem was gradually decreased while heating, and under a reducedpressure of 133 Pa, at 290° C., polymerization was performed whilestirring and distilling ethylene glycol off. When the degree ofpolymerization reached the equivalent of an intrinsic viscosity of 0.62,the system was purged with nitrogen and the pressure was returned to theatmospheric pressure. Next, 0.003% by weight of potassium acetate and anethylene glycol solution of hexamine in a predetermined amount werethoroughly mixed and added to the reaction system. The pressure of thereaction system was gradually decreased, and under a reduced pressure of133 Pa, at 290° C., polymerization was performed again in the samemanner as that described above. When the degree of polymerizationreached the equivalent of an intrinsic viscosity of 0.62, a polymer wasdischarged, and a polyester composition with an intrinsic viscosity of0.60 was thereby obtained. The results thereof are shown in Table 4. InTable 4, the amount of metal added means the amount of metal addedbefore repolymerization, and the metal content means the amount of metalin the resultant polyester composition. The difference between theamount of metal added and the metal content corresponds to the amount ofmetal removed. By using nitrogen as donor atoms, the germanium ioncontent was significantly decreased, germanium being a transition metal.

Metal ions and ligands were separated and recovered from the distillate,which was retrieved from the system in the polycondensation step, by amethod described below After HNO₃ was added to the distillate so as tosatisfy pH=1.5, water, low-boiling point components, and ethylene glycolwere removed by distillation at 210° C. at 1,330 Pa for 4 hours, and asolid residue was separated. Into the low-boiling point components, 400parts by weight of ethanol, 3 parts by weight of potassium acetate, and10 parts by weight of activated carbon were added, followed by mixing atroom temperature. Impurities generated were filtered out, and 1,000parts by weight of water were added to the filtrate. A precipitatedsolid was then separated by filtration, and cleaning was performed withwater and ethanol, followed by drying. A white powder (hexaamine) wasthereby obtained. To the solid residue, 100 parts by weight of purifiedwater was added, and the solid residue was dissolved by heating at 95°C. at atmospheric pressure for 2 hours. Insoluble components werefiltered out at 50° C. using a membrane filter (5.0 μm). The filtratecontained 500 ppm, calculated on the basis of germanium atomic weight,of the germanium catalyst, 50 ppm of the magnesium catalyst, and 300 ppmof the potassium catalyst. The resultant filtrate was condensed at 95°C. at 55,000 Pa for 2 hours and an aqueous solution containing 1.5% byweight of germanium, 0.9% by weight of potassium, and 0.15% by weight ofmagnesium was formed. Acetic acid and ethylene glycol (EG) were addedthereto and azeotropic distillation was performed to form an EG solution(mixed catalyst) containing 4.5% by weight of germanium, 1.8% by weightof potassium, and 0.45% by weight of magnesium.

Example 22

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.038% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product. The mixed catalyst recovered in Example 21was added thereto so that the amount of potassium acetate was 0.003% byweight, and 0.0042% by weight of germanium dioxide was further addedthereto. The mixture was transferred to a polycondensation reactionvessel. Next, the pressure of the reaction system was graduallydecreased while heating, and under a reduced pressure of 133 Pa, at 290°C., polymerization was performed while stirring and distilling ethyleneglycol off. When the degree of polymerization reached the equivalent ofan intrinsic viscosity of 0.62, the system was purged with nitrogen andthe pressure was returned to the atmospheric pressure. An ethyleneglycol solution of the hexaamine recovered in Example 21 was preparedand thoroughly mixed and a predetermined amount thereof was added to thereaction system. The pressure of the reaction system was graduallydecreased, and under a reduced pressure of 133 Pa, at 290° C.,polymerization was performed again in the same manner as that describedabove. When the degree of polymerization reached the equivalent of anintrinsic viscosity of 0.62, a polymer was discharged, and a polyestercomposition with an intrinsic viscosity of 0.60 was thereby obtained.The results thereof are shown in Table 4. In Table 4, the amount ofmetal added means the amount of metal added before repolymerization, andthe metal content means the amount of metal in the resultant polyestercomposition. The difference between the amount of metal added and themetal content corresponds to the amount of metal removed.

Example 23

Into a mixture of 100 parts by weight of dimethylterephthalate and 60parts by weight of ethylene glycol, 0.04% by weight of magnesiumacetate, relative to the amount of dimethylterephthalate, was added, andmethanol was distilled off by heating to perform transesterification.The completion of transesterification was determined by the amount ofthe methanol distillate. Next, 0.020% by weight of trimethyl phosphate,relative to the amount of dimethylterephthalate, was added to thetransesterification product, and then 0.007% by weight of antimonytrioxide was added thereto. The mixture was transferred to apolycondensation reaction vessel. Next, the pressure of the reactionsystem was gradually decreased while heating, and under a reducedpressure of 133 Pa, at 290° C., polymerization was performed whilestirring and distilling ethylene glycol off. When the degree ofpolymerization reached the equivalent of an intrinsic viscosity of 0.62,the system was purged with nitrogen and the pressure was returned to theatmospheric pressure. Potassium acetate in the amount of 0.03% by weightand an ethylene glycol solution of hexaamine in a predetermined amountwere thoroughly mixed and added to the reaction system. The pressure ofthe reaction system was gradually decreased, and under a reducedpressure of 133 Pa, at 290° C., polymerization was performed again inthe same manner as that described above. When the degree ofpolymerization reached the equivalent of an intrinsic viscosity of 0.62,a polymer was discharged, and a polyester composition with an intrinsicviscosity of 0.60 was thereby obtained. The results thereof are shown inTable 4. In Table 4, the amount of metal added means the amount of metaladded before repolymerization, and the metal content means the amount ofmetal in the resultant polyester composition. The difference between theamount of metal added and the metal content corresponds to the amount ofmetal removed.

Example 24

A polyester composition was obtained in the same manner as that ofExample 15 apart from the fact that the amount of 18-crown-6 added was0.025% by weight and a predetermined amount of hexaamine was added. Theresults thereof are shown in Table 4.

Comparative Example 7

A polyester composition was obtained in the same manner as that ofExample 15 apart from the fact that 18-crown-6 was not added. Theresults thereof are shown in Table 4. In Table 4, the amount of metaladded means the amount of metal added before repolymerization, and themetal content means the amount of metal in the resultant polyestercomposition.

TABLE 4 Amount Ligand of content ligand Number wt % (to % BB of Amountof metal (to Metal) 3 6 donor Amount added (ppm) Content (ppm) Ligandpolyester) Rma, Rmt hrs hrs atoms Ge Sb Mg K Ge Sb Mg K Example 1518-crown-6 0.2 Rma = 0.38 0.58 6 50 45 120 35 30 60 1.5 Example 1618-crown-6 0.2 Rma = 0.38 0.59 6 50 45 120 40 35 70 1.5 Example 17Dibenzo18- 0.2 Rma = 0.39 0.61 6 60 45 120 50 30 80 crown-6 1.1 Example18 Dibenzo30- 0.2 Rma = 0.38 0.65 10 50 45 120 40 25 40 crown-10 0.75Example 19 12-crown-4 0.2 Rma = 0.31 0.51 4 50 45 35 35 6.0 Example 2015-crown-5 0.2 Rma = 0.41 0.64 5 50 45 120 35 35 100 1.8 Example 21Hexaamine 0.05 Rmt = 5 0.34 0.53 4 50 45 12 20 40 11 Example 22Hexaamine 0.05 Rmt = 5 0.34 0.54 4 50 45 12 25 40 11 Example 23Hexaamine 0.034 Rmt = 5 0.33 0.53 4 60 45 12 40 40 11 Example 24Hexaamine 0.025 Rmt = 2.5 0.38 0.57 4 50 45 120 25 30 80 18-crown-6 0.16Rma = 2.5 6 Comparative — 0.0 0 0.44 0.71 0 60 45 120 60 40 100 Example7

INDUSTRIAL APPLICABILITY

The polyester composition and film of the present invention are suitablefor various applications, such as for magnetic materials, packagingmaterials, optical materials, and electric materials because ofexcellent heat resistance, colorability, and weathering resistance.

In accordance with a method for producing a polyester composition of thepresent invention, it is possible to remove metal catalysts, whichadversely affect heat resistance, without decreasing electrostaticadhesion between a molten film and a casting drum. Consequently, it ispossible to produce polyester compositions at high productivity.Moreover, in accordance with the method for producing the polyestercomposition of the present invention, it is possible to recovercatalysts, and thus production costs can be reduced.

1. A polyester composition comprising a polyester and a ligandcoordinated to a metal ion, wherein the ligand is a clathrate compoundand comprises at least one donor atom selected from the group consistingof a nitrogen atom, a sulfur atom, and an oxygen atom, the polyestercomposition having a melt resistivity of less than 15×10⁷ Ω·cm.
 2. Apolyester composition according to claim 1, wherein the ligand is atleast one compound selected from the group consisting of linearpolyether amides, cyclic polyethers, linear polyethers, cyclic polyetherpolyesters, cyclic polyketones, cyclic polyamines, cyclic polyaminepolyamides, cyclic polythiaethers, azacrown ethers, thiacrown ethers,cyclic azathiacrown ethers, azathiacrown ethers, bicyclic cryptands,tricyclic cryptands, spherical cryptands, linear polyamines, andphosphorus sulfide.
 3. A polyester composition according to claim 1,wherein the number of donor atoms contained in the ligand is 4 to
 20. 4.A polyester composition according to claim 1, wherein the metal or metalion is at least one element selected from the group consisting oflithium, sodium, potassium, rubidium, cesium, beryllium, magnesium,calcium, strontium, barium, iron, antimony, titanium, aluminum,germanium, manganese, cobalt, zinc, copper, nickel, cadmium, and tin. 5.A polyester composition according to claim 1, wherein a melt resistivityR0 before the addition of the ligand and a melt resistivity R after theaddition of the ligand satisfy the relationship R/R0≦1.3.
 6. A polyestercomposition according to claim 1, the polyester composition comprisespolyethylene terephthalate or polyethylene-2,6-naphthalate.
 7. A filmcomprising a polyester composition according to claim
 1. 8. A laminatedfilm comprising at least one layer of the film according to claim 7.